Sample Azure pipelines template for extracting the node version from the package.json's engine setting

azure-pipelines.yaml

steps:
  - bash: |
      set -euo pipefail
      version=$( jq --raw-output '.engines.node' ./package.json)

      echo "##vso[task.setvariable variable=nodeVersion;isOutput=true]$version"
    displayName: Get node version from package.json
    name: getNode
  - task: NodeTool@0
    displayName: Use node version from package.json
    retryCountOnTaskFailure: 1
    inputs:
      versionSpec: $(getNode.nodeVersion)